DE2714666A1 - GAS LASER - Google Patents

Description

DR. IrEKG DIFL ING. STAPF DIPL-ING. SCHWABE DR. DR. SANDMAIR

PATENTANWÄLTE, ι, ^, - ο

8 MUNICH 86, POST BOX 86 02 4S

Lawyer file: 27 97β

United Kingdom Atomic Energy Authority London SWlY ^ QP / Great Britain

Gas laser

The invention relates to gas lasers and, more particularly, to gas discharge lasers with a cross excitation.

According to the invention, a gas laser with a gas mixture with carbon dioxide as the laser medium is created, the laser medium is cooled to such a temperature that the thermal occupation of the lower energy level an output laser transition between a higher energy level and a lower energy level of the carbon dioxide molecule is reduced, and wherein the laser medium is initially energized to produce a translation inversion.

vii / xx / ha 709841/0932

(0 (9) 98 82 72 8 Munich 80, Mauerkircherstraße 45 Banks: Bayerische Vereinsbank Munich 453 100

987043 Telegrams: BERGSTAPFPATENT Munich Hypo-Bank Munich 3892623

983310 TELEX: 0524SW BERG d Postscheck Munich 65343-808

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gene, which leads to the laser transition with such a value that a significant thermal population of the lower Energy levels is avoided.

In a preferred embodiment of the invention, at the laser a transition between the 02 0 and 01 O vibrational energy levels of the carbon dioxide molecule is used as the source of the laser radiation, and the laser medium is a mixture or a mixture of one or more of the gases hydrogen, helium or argon together with nitrogen and carbon dioxide. That N / CO ratio is chosen so that it is ~ 9, that is, it is higher than the ratio commonly used in gas lasers with carbon dioxide as the laser medium to pump the symmetrical (and) CO bending mode or the corresponding vibration type with regard to the antisymmetrical CO and N vibration types. The hydrogen, helium and / or argon admixture is selected to be around the 01 O energy level of the carbon dioxide molecule to loosen or decrease, but the optimal ratio of these gases changes with the total pressure as a result a butt coupling between the 01 0, 10 ° 0, 02 0 and 02 ° 0 levels and practical considerations such as from Thermal effects associated with certain types of pre-ionization

_are to be reduced or reduced

The invention is described below on the basis of a preferred embodiment with reference to the accompanying drawings in

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individually described. Show it:

1 shows a schematic representation of a gas laser according to the invention; and

Fig.2 schematically shows the important energy transitions in the laser of Fig.1.

In FIG. 1, a gas laser with transverse excitation, in which a mixture of carbon dioxide, nitrogen and helium (or other additives) is used as the laser medium, has a closed line system 1 which has an area 2 with plane-parallel or other / corresponding surfaces which laser radiation can be obtained or subtracted. The line system 1 has a circulation pump 3 and a heat exchanger k . An exciting gas discharge 7 is maintained in area 2 of the line system by anode and cathode electrodes 5 and 6, respectively. The discharge 7, which is maintained transversely to the direction of the gas flow 7 in the line system 1 and transversely to the direction of the emitted laser radiation, is the energy source which is used to generate the laser radiation. Above or in the direction of flow in front of the electrodes 5 and 6, a baffle plate or plate 9 is provided, which creates uniform turbulence conditions in the laser medium flowing into the discharge region 2.

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The laser medium is a mixture of carbon dioxide (C 0), nitrogen and helium with volume ratios of about 1: 9 ^: 10 · Ks is the discharge area 2 with a pressure of about 0.1 to 0.6 ata (absolute pressure in atmospheres) and at a temperature in the range from 140 to 230 K. The laser medium is ionized in that an additional or auxiliary electron beam with an energy of up to 2 * 10 keV passes through a 0.025 cm thick titanium foil for a period of about 10 microseconds in order to generate or absorb energy from about 150 to 200J / Liter atmospheres (J / liter atmospheres) from the main (pump capacitors. Neither the foil nor the electron beam is shown in the drawing; however, the foil must of course be placed where the electron beam can create a corresponding ionization source, On the other hand, pulsed ultraviolet ionization in conjunction with an appropriate lightly ionized organic additive such as trimethylamine can be used for the same purpose.

The electrodes 5 and 6 are clocked accordingly Impulse operation with a current impulse duration of a few tens of microseconds operated. (This pulse length is long enough to remove carbon dioxide (001) and the To pump nitrogen to ν = l vibrational energy levels, and to do so slowly enough for the subsequent population inversion.

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sion between the carbon dioxide "(02 0 and 01 O) vibrational energy levels so that they are not lost as a result of the lower energy level that is thermally occupied). When the carbon dioxide has been excited, this results in the almost simultaneous sequential pulse emission of coherent radiation at wavelengths of 9 »^ to 9» 6yum and l6.2, by reduced, which comes from the (vibrational) energy transitions (00 I) - (02 0) or (02 ⁰ O) - (01 ¹ O).

The 9 »^ to 9» 6 .mu.m long pulse can be created by an auxiliary or additional TEA laser of an intensity sufficient to saturate the (00 I) - (02 O) transition of the carbon dioxide and um have a duration in the range of 1 to 300 nsec. This method allows independent control of the initial excitation and subsequent inversion to the 16 µm junction. The 16.2 µm long output pulse then has a small signal amplification coefficient Λύλ ^ ^{x 10 cm} > and under optimal conditions the overall efficiency is greater than 0.2?% · In general, the 9 »6yum and 16.2 µm long pulses must have a duration of j £ (30 / p) nsec, where ρ is the total pressure in atmospheres.

The laser is operated in pulse mode, with both the laser medium relatively weak, i.e. it can be pumped slowly, in order to achieve a thermal occupation of the (01 0) oscillation energy level to avoid, which would otherwise have the necessary

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inversion would destroy, as well as the transition type of the 9.6 / µm long pulse and the subsequent 16.2 µm long output pulse avoids shock de-excitation of the population inversions.

The described embodiment of the invention is straightforward Can be dimensioned and interpreted in such a way that operation in a large peak and medium power range is possible. She can also be at Pressures of at least 1 atmosphere can be operated (in order to create a broadband amplifier operation with low gas consumption). The addition or replacement of other isotope modifications of carbon dioxide (such as COO, CO or CO) generally extends the tuning range of the laser; however, the possibility of a "near absorption match" i.e. the possibility that another energy level will be reached, from the rotation multiple in particular of the basic vibration state (00 O) and in general of other lower levels through a wise choice of parameters be avoided. An example is given to illustrate this; at wavelengths near or near

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in the CO H (13) laser transition, an amplifier operating on a pure C 0 ^ component should be operated at the lowest practicable temperature at a total pressure of / ^ - 0.2 atmospheres to avoid undesirable absorption by the p - Avoid (26) ground state (00 0 to 01 O) transition λ, χι. Conversely, when printing is on the order of

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1 atmosphere also an increase or a strengthening of some

2 1

(02 0) to (Ol O) transitions as a result of the collision occupation of the (02 0) Levels present or can be maintained under favorable kinetic conditions.

As a narrow-band laser oscillator, the system can be used effectively in a range of discrete thermal vibrational transitions with some of the isotopic variants of CO at pressures in general

- 1 -2
in the range of 10 to 10 atmospheres, that is, operated at pressures sufficiently low to ensure and ensure that the life (ί ") of the settling or transient inversion is long enough to separate oscillation from the noise level can build up to a saturation;. to ensure this, the product ° O ^C ^ * ^e i should exceed ^NEN factor of about 30, where c is the speed of light is possible Beinahkoinzidenzen with absorbent transitions from the (00 0) ground state again form a additional upper limit on the total pressure: for example, the (02 0) to (01 ¹ O) -C ¹ ^ OR (13) transition can be generated at a total pressure of about 10 atmospheres, but the R (l5) and R (17) - Transitions would require lower pressures accordingly.

Claims

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Claims (1)

2 7 K ö 6 6 - * - Claims 1. Gas laser with a gas mixture with carbon dioxide as the laser medium, characterized in that the laser medium is cooled to such a temperature that the thermal Occupying the lower energy level of an output laser transition between a higher energy level and one The lower energy level of the carbon dioxide molecule is reduced, and that the laser medium is initially excited to cause the degradation inversion to create which leads to the laser transition at such a value that a significant thermal population of lower energy levels is avoided. 2. Gus laser according to claim 1, characterized in that that the laser transition takes place between the (02 O) and (01 O) vibrational energy levels of the carbon dioxide molecules. 3. Gas laser according to one of claims 1 or 2, characterized in that the laser medium has a discharge region (2) of the laser at a temperature in the range of approximately ΙΊΟ to 23O ° K supplied wiri. k. Gas laser according to one of Claims 1 to 3, characterized in that the laser medium contains carbon dioxide 7ÜH841 / 0932 ~ ⁹ ~ • t. sanun with a mixture of nitrogen and one or more the gases contain hydrogen, helium and argon. 5. Gas laser according to claim 5 »characterized in that the volume ratio of nitrogen to carbon is greater than is 9. 6. Gas laser according to one of the preceding claims, characterized in that the laser medium is a mixture or a mixture of carbon dioxide, nitrogen and helium in the volume ratios of 1: 9 ^: 10. 7. Gas laser according to one of the preceding claims, characterized in that the laser medium initially through a pulse-controlled electrical discharge is excited, the duration of the pulses being on the order of ten microseconds lies. 8. Gas laser according to claim 7 »characterized in that that the excited laser medium with radiation pulses with a wavelength in the range of 9 »^ to 9i6 to an intensity is irradiated, which is sufficient to the (00 l) to (02 O) transition of the carbon dioxide molecule, and with a duration which is approximately equal to or less than 30 / p nsec, wherein ρ is the total pressure (in atmospheres) of the laser medium. 709841/0932 " ¹⁰ " 2 7 I U b 6 6 • 3 . 9- gas laser according to one of claims 1 to 8, characterized in that the laser medium has such a pressure that the product ° < _n ^c ^ should exceed a value of about 30, where o (is the small signal gain, c is the Is the speed of light and 7 is the lifetime of the transition translation inversion which leads to the laser transition. 10. Gas laser according to one of the preceding claims, characterized in that the laser medium is at a total pressure ranges from about 0.1 to 0.6 atmospheres. 11. Gas laser according to one of claims 1 to 8, characterized in that the laser medium is at a total pressure until about one atmosphere lies. 12. Gas laser according to one of the preceding claims, characterized in that the laser medium is ionized, before it is excited to sound the transition population inversion which leads to the laser transition. 13 · Gas laser still claim 12, characterized thereby e t that the laser medium is ionized by sending a pulsed additional electron beam through a metal foil passes through through which the laser medium has to flow. 709841/0932 27U666 -At- ' H- lk. Gas laser according to Claim 12, characterized in that the laser medium is ionized by means of a pulse-controlled beam of ultraviolet radiation. 15. Gas laser according to claim 12, characterized in that that the pulse-controlled beam of ultraviolet radiation in conjunction with a slightly ionized, organic Additive such as trimethylamine is used. 16. Gas laser according to one of the preceding claims, characterized characterized in that the carbon dioxide has molecules which are isotopic variants of natural carbon dioxide are. 17. Gas laser according to claim l6, characterized in that that the lasing medium has molecules of C 0 and that the total gas pressure is less than 0.2 atmospheres. 18. Gas laser according to claim l6, characterized in that that the total pressure of the laser medium is about 10 ~ atmospheres. 709841/0932